1. Field of the Invention
This invention relates to an electronic musical instrument provided with a tonality designation device, and in particular, to an electronic musical instrument in which the tonality designation is performed based on key depression in a keyboard of the instrument.
2. Prior Art
Musical tone producing methods in prior art electronic musical instruments having a tonality designation device are generally classified to: (1) a method in which with a tonality having been designated in advance, chords and bass tones related to the designated tonality and melody tones are formed by the performance of the melody tones, and these chords and bass tones are produced together with the melody tones (for example, as disclosed in the U.S. Pat. No. 3,986,424 to Sakashita, issued on Oct. 19, 1976), (2) a method in which with the tonality having been designated in advance, second melody tones related to designated tonality and first melody tones are formed by the performance of the first melody tones performed in monotones, and the second melody tones are produced together with the first melody tones (for example, as disclosed in the U.S. Pat. No. 4,205,576 to Deutsch et al., issued on June 3, 1980) and (3) a method in which information indicating the progress of chords memorized in advance according to a designated tonality and the progress of the automatic rhythm performance is read out, chords and bass tones are formed based on the information, and these tones are sequentially produced (for example, pending U.S. Pat. application Ser. No. 161,582 now U.S. Pat. No. 4,327,622).
Each of the above-mentioned electronic musical instruments has a tonality designation switch corresponding to each tonality, and a tonality to be performed is designated by turning on one of these tonality designation switches. These tonality designation switches are provided on the operation (control) panel of the electronic musical instrument. Since many switches for selecting a variety of functions are arranged on the operation panel, the addition of the tonality designation switches lowers operatability of the musical instrument to a great extent. Further, due to the considerably large number of these switches, which is as many as the number of tonalities, are required, a high cost is resulted unavoidably.